A Reversible Data Hiding Scheme Using Pixel Location

In this paper, authors propose a new reversible data hiding scheme that has two passes. In first pass, the cover image is divided into non-overlapping blocks of 2×2 pixels. The secret data bit stream is converted into 2-bit segments, each representing one of the four values, i.e., 0,1,2,3 and these digits (2-bit segments) are embedded into blocks by increasing/decreasing the pixel value of the block by 1. If the pixel is even valued, then the pixel is increased otherwise it is decreased by 1 to embed the secret data. In second pass, the same process of the first pass embedding is repeated. The second pass embedding helps in achieving better stego-image quality and high data hiding capacity because some of the pixels changed in first pass are recovered to their original form. Basically, the second pass is a complement of the first pass. This scheme can achieve approximately 1 bpp data hiding capacity and more than 55db Peak Signal-to-Noise Ratio (PSNR) for all cover images in our experiments. For ensuring reversibility of the scheme, a location map for each phase is constructed and embedded into the image. Though, the scheme has some overhead in hiding the secret data, yet it provides good quality with high capacity. Since it only increases/decreases the pixel value of at most half of the pixels, it is very simple. The experimental results show that it is superior to the state of the art schemes